Solvothermal depolymerization and recrystallization of imine-linked two-dimensional covalent organic frameworks

Woojung Ji, Leslie S. Hamachi, Anusree Natraj, Nathan C. Flanders, Rebecca L Li, Lin X. Chen, William R. Dichtel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Mechanistic understanding into the formation and growth of imine-linked two-dimensional (2D) covalent organic frameworks (COFs) is needed to improve their materials quality and access larger crystallite sizes, both of which limit the promise of 2D COFs and 2D polymerization techniques. Here we report a previously unknown temperature-dependent depolymerization of colloidal 2D imine-linked COFs, which offers a new means to improve their crystallinity. 2D COF colloids form at room temperature but then depolymerize when their reaction mixtures are heated to 90 °C. As the solutions are cooled back to room temperature, the 2D COFs repolymerize and crystallize with improved crystallinity and porosity, as characterized by X-ray diffraction, infrared spectroscopy and N2porosimetry. The evolution of COF crystallinity during the solvothermal depolymerization and repolymerization processes was characterized byin situwide angle X-ray scattering, and the concentrations of free COF monomers as a function of temperature were quantified by variable temperature1H NMR spectroscopy. The ability of a 2D COF to depolymerize under these conditions depends on both the identity of the COF and its initial materials quality. For one network formed at room temperature (TAPB-PDA COF), a first depolymerization process is nearly complete, and the repolymerization yields materials with dramatically enhanced crystallinity and surface area. Already recrystallized materials partially depolymerize upon heating their reaction mixtures a second time. A related 2D COF (TAPB-DMTA COF) forms initially with improved crystallinity compared toTAPB-PDA COFand then partially depolymerizes upon heating. These results suggest that both high materials quality and network-dependent properties, such as interlayer interaction strength, influence the extent to which 2D COFs resist depolymerization. These findings offer a new means to recrystallize or solvent anneal 2D COFs and may ultimately inform crystallization conditions for obtaining large-area imine-linked two-dimensional polymers from solution.

Original languageEnglish (US)
Pages (from-to)16014-16022
Number of pages9
JournalChemical Science
Volume12
Issue number48
DOIs
StatePublished - Dec 28 2021

Funding

We acknowledge the Army Research Office for a Multidisciplinary University Research Initiatives (MURI) award under grant number W911NF-15-1-0447. Parts of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and the Dow Chemical Company. This research used resources of the Advanced Photon Source and Center for Nanoscale Materials, both U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC0206CH11357. This work has also made use of the IMSERC, EPIC, and Keck II facility of NUANCE Center at Northwestern University, which has received support from the So and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS1542205), the MRSEC program (NSF DMR-1720139) at the Materials Research Center, the Keck Foundation, the State of Illinois and International Institute for Nanotechnology (IIN). N. C. F. and L. X. C. are partially supported by Basic Energy Science, CBG Division, US Department of Energy through Argonne National Laboratory under Contract No. DE-AC0206CH11357. We acknowledge the Army Research Office for a Multidisciplinary University Research Initiatives (MURI) award under grant number W911NF-15-1-0447. Parts of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and the Dow Chemical Company. This research used resources of the Advanced Photon Source and Center for Nanoscale Materials, both U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC0206CH11357. This work has also made use of the IMSERC, EPIC, and Keck II facility of NUANCE Center at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS1542205), the MRSEC program (NSF DMR-1720139) at the Materials Research Center, the Keck Foundation, the State of Illinois and International Institute for Nanotechnology (IIN). N. C. F. and L. X. C. are partially supported by Basic Energy Science, CBG Division, US Department of Energy through Argonne National Laboratory under Contract No. DE-AC0206CH11357.

ASJC Scopus subject areas

  • General Chemistry

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